1. Field of the Invention
The present invention relates to electronic apparatus provided with a mode setting switch and being capable of preventing misoperation in a device such as a calculator. For example, in a calculator and the like a misoperation occurs sometimes when key codes once stored in a key buffer are derived from the key buffer to process the key codes. The present invention is directed to a solution of such problem by storing also the operational status of the mode setting switch at the time when the key entry was made.
2. Description of the Prior Art
In view of size, desk-top calculators are classified into three groups, that is, small type, middle type and large type calculators. Generally, the small type calculator is not provided with a key buffer and thus the input of a key is valid only when the control phase is just in a status of waiting for reading-in of the key information. However, the middle and large type calculators are provided with a buffer memory in which information of successive keying is stored for a time. Such key information stored in the buffer memory can be derived from it later at any desired time. In this case, there is a time lag between the input of information by keying and the derivation of the key information. In such type of calculators, there may be used a mode setting switch for setting various modes of operation for processing the input data, and the combination use of the status of the mode setting switch and the key information are designed to provide various different functions. In this case, since there is a time lag between the time when the input of information is entered by keys and the time when the derivation of the key information is made, and the status of the mode setting switch will be changed during the time, the status of the mode setting switch at the time when the key information is derived from the buffer will be different from that at the time when the key information is entered.
The above fact gives some inconvenience for such type of calculator which has various different functions in accordance with different combinations of the status of a mode setting switch and the keys. Sometimes, the calculator will function differently from what the operator expects at that time.